The present invention relates generally to radio frequency identification (RFID) systems. More particularly, the invention relates to a modular RFID antenna and configuration system.
RFID systems are well known in the art. Such systems include relatively large packages containing battery powered transmission/receiving circuitry, such as the identification system disclosed in U.S. Pat. No. 4,274,083, to passive systems in which the transponder receives its power from the base station or interrogator, such as the identification system disclosed in U.S. Pat. No. 4,654,658.
A typical RFID system is made up of reusable tags fixed to or embedded in product carriers, an antenna system that interrogates the tags via an RF link and a controller. The host (or computer) system interfaces with the controller and directs the interrogation of the tags.
The RFID system thus provides effective means of identifying, monitoring, and controlling materials in a closed loop process. In a factory environment, the tags are employed as the transport mechanism between xe2x80x9cislands of automation,xe2x80x9d providing a record of each process which can be acted upon immediately or downloaded later for analysis.
In operation, as a tag passes near an RFID antenna unit, an antenna emits RF signals towards the tag. The emitted RF signals induce a current in the tag. The current powers-up the tag, thereby enabling the tag to transmit response signals from the tag to the antenna unit.
The tags can also be powered by an internal battery (i.e., an xe2x80x9cactivexe2x80x9d tag). The life span of an active tag is, however, generally limited by the lifetime of the battery.
RFID antenna units are typically placed on gate like structures in manufacturing environments and are used to read tagged items as they passed through. The antennas are generally operated in the ranges of 2.45 GHz, 900 MHz or 125 KHz. The noted frequencies are employed to achieve a longer antenna field range.
It is, however, well known that at 2.45 GHz and 900 MHz the fields produced by the antenna(s) are affected by virtually everything that passes through the field, including metals and moisture. Metal causes extreme reflection of the fields, while moisture causes extreme absorption of the field. Therefore, any metal object or anything containing moisture, such as the human body, will cause extreme disruption of the field and, hence, the communication of the antenna with the tags.
In an effort to eliminate or substantially reduce the extreme reflection cause by metal objects passing through the field, multiple reflective shields have been employed. The shields cause the field to continuously reflect until it eventually contacts a tag. This is, however, a costly and often impractical solution.
At the other extreme (i.e., 125 KHz), better environmental performance is achieved because metal and moisture generally have less affect on the field. There are, however, several significant drawbacks associated with the noted operating frequency. A major drawback is the high cost, since 100 or more turns in the antenna coil are required to achieve the 125 KHz operating range.
Alternatively, an operating frequency of 13.56 MHz can be employed. Although the noted frequency achieves good environmental performance, it is often unable to achieve the operating range of the aforementioned frequencies.
It is therefore an object of the present invention to provide an RFID antenna system that utilizes modular antenna segments that can be connected in a variety of configurations for multiple applications.
In accordance with the above objects and those that will be mentioned and will become apparent below, the modular RFID antenna system in accordance with this invention comprises modular RFID antenna segments that can be connected in multiple configurations to allow multi-directional (i.e., omni-directional) RF communication to at least one transponder or tag located on one or more items that pass through the field of the antenna system. The modular RFID antenna system further includes a configuration system that allows the user to customize, order, configure, test and operate a modular RFID antenna system for a particular application.